Backend: menu_pages CE will throw an error when it contains references to deleted pages
Since version 10.4.15 the TYPO3 backend will throw an exception in the page module when the page contains a "menu_pages" content element that has a reference to a deleted page. This issue was introduced with commit 79e4001edf54f1996b33b5f02a5497f8edce9bc2. Other TYPO3 versions may be affected as well.
How to reproduce:
1) Create a menu_pages content element
2) Select pages
3) Save element
4) Delete one of the previously linked pages
5) Open the page containing the menu_pages element
See attached screenshot for any further details.